This is a Viking historical romance written perhaps in the 1980s. The heroine was betrothed to the hero who was the son destined to inherit. She was blinded and deaf following a trauma in her youth. The hero did not want to marry her and stayed away for as long as he could. He returned and met her without recognizing her. He decided to make her his mistress without realizing who she was. She had a dog Bragging I think was the name of the dog. When she sleep walks, she can see, speak and hear.
Eventually, she regained her ability to hear and speak and at the end, her sight as well. There was a portion of the book when they seemed to be on a quest or long journey through a snow bound forest.